Originally posted by redgreen999:

I believe the more trolls you kill, the more trolls you get during the raid.

I also believe this.

I had my current world's only troll raid when I already had a very good knife that killed trolls in mere seconds. I ended up getting six trolls during the raid, when it's always been two or three in the past when I've killed them slower.


And to complete the answer to the OP's last question: no, your base cannot be raided while you're away.
The raids will only spawn where you are, if their conditions are met there.

I don't have a moat around my base, and even when I had stakewall instead of stone walls around it nothing ever managed to break through the wall.
Key is to leave the base instantly when a raid starts, as it takes a few moments for the mobs to show up.
("Cold wind from the mountains" I would expect is an exception to that last bit. I've not had it yet in this world.)